As baseline method we consider the AE in [1]}. However, differently from what has been proposed by the authors, and to further boost the performance, we do not consider a uniform quantization of the latent space but rather a quantization based on the k-means algorithm, where the k-means is run once for each latent space unit. In particular, if \(B\)  bits are available for the feedback quantization, each element of the latent space is quantized with \(B/M\)  bits. A similar approach has been considered also in [2]}. The performance of the baseline method has been evaluated also with the bit allocation algorithm described in Section . However, in this case, the bit allocation algorithm did not improve the result because of the lack of a proper ranking over the latent space units of the AE.
